The problem of substrate sensitivity has been known in the art and efforts at its control by the introduction of impurities in the semiconductor have been undertaken for some time in various structures.
U.S. Pat. Nos. 3,449,644; 3,585,463 and 3,829,885 all involve the introduction of gold as an impurity in different types of semiconductor structures in order to improve the design, operation and performance of the devices. A problem, however, is present in that an impurity such as gold tends to diffuse rapidly and hence to migrate during hot processing steps and in use under all but fairly low operating temperatures.